Alien Breed 3: Descent Trophies
Elite Unit
Complete all single player levels 1-5 on elite difficulty.

Elite is unlocked for you right from the start, but it is recommended you play on Elite on a second playthrough as the other trophies are easier to earn on a lower difficulty setting.

Some tips:

Use the Blaster whenever you can, especially on the Larvals to save ammo. Save the other weapons for the larger enemies.
Credits should only be used for ammo and Health Kits if you think it's necessary. You'll run across enough Health Kits that you should hardly have the need to purchase them from Terminals. Save your credits for upgrading your weapons or Hardened Armor instead.
Damage Upgrade on weapons and the Medi Stimulant upgrade is a must. It will save you a lot more ammo and kill your enemies much faster, especially when they gang up on you. Go for the Assault Rifle first.
Use doorways or run to the other end of a corridor so youre at a more advantageous position in taking out your aliens. If you get ganged up on, make good use of your Stun Grenades.
Explore rooms as youre going from waypoint to waypoint for ammo, credits, health kits. This will allow you to save up on credits for more useful things like Upgrades.

Then again, this is the third time youve had to do an Elite run so Im sure you guys know the procedure already